Surface acoustic wave-based sensing and actuation of contamination

ABSTRACT

A method includes producing a first surface acoustic wave (SAW) on a magnetic head slider using a first interdigitated transducer (IDT), wherein the SAW has a first set of wave characteristics. The method also includes receiving the first SAW at a second IDT on the magnetic head slider. The method also includes analyzing the SAW for a second set of wave characteristics. The method also includes determining, based on the analyzing, that a substance having at least one characteristic is located in a path of the SAW on the magnetic head slider.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 16/369,297, filed Mar. 29, 2019, now allowed, which claims thebenefit of U.S. Provisional Patent Application No. 62/659,181, filedApr. 18, 2018 and titled “Surface Acoustic Wave-Based Sensing andActuation of Contamination”, the entire contents of which areincorporated herein by reference in their entireties.

BACKGROUND

The present disclosure relates to aspects of magnetic head sliders(“sliders”) within hard-disk drives (HDDs), and relates in particular toimproved slider performance.

HDDs are data storage devices that include one or more rotatable disksto which data is written and read by way of one or more magneticread/write heads that are movably supported with respect to surfaces ofthe disks by a like number of head suspension assemblies, which aretypically movably supported relative to a respective disk surface sothat a magnetic read/write head can be selectively positioned relativeto a circular data track of the disk surface. Such head is typicallyprovided on an aerodynamically-designed slider so as to fly closely, ata so-called “fly height,” of several nanometers above the disk surfacewhile the disk is spinning. Each slider can be aerodynamically shaped tohave various surfaces, including an air-bearing surface (ABS), whichfaces the spinning disk. The slider may also have a trailing edge (TE),which follows or “trails” the ABS with respect to the relative movementof the slider and the magnetic disk surface. Each head suspensionassembly is normally connected to a rotatable drive actuator arm andload beam for rotatably moving a slider for data writing and readingduring HDD operation. Sliders, as used herein (in conjunction with aspinning disk surface), may form what are referred to as advanced airbearings (AABs).

Disk surfaces have experienced increasing data density per unit area,known as areal density, as HDDs have continued to increase in storagecapacity. Specifically, individual data tracks on the disk surfaces havebecome narrower and the radial spacing between tracks has decreased.Technologies such as heat-assisted magnetic recording (HAMR) andshingled magnetic recording (SMR) have led to greater areal density andcloser-spaced data tracks. An increasing desire and need for magnetichead read/write precision in conjunction with smaller fly heights hasled to greater magnetic read/write sensitivity and slider proximity tothe disk surfaces.

An HDD assembly is typically a tightly-sealed structure. Duringassembly, an HDD is produced in an environment where minimal foreignparticles and/or contaminants enter the HDD. However, contaminationmight get in during assembly or eventually enter an HDD, includingcontamination that can settle on sensitive disk or slider surfaces.Lubricant liquid and/or droplets may also be present on varioussurfaces, sometimes intentionally, and are included in the intendedscope of “contaminants,” for the purposes of this disclosure.Contaminants may take the form of liquids, droplets, films, orotherwise. With recent developments, including increasing areal densityand reduced slider fly height and increased head precision,contamination (e.g., droplets) had not typically been problematic to aslider during HDD operation. With shrinking fly heights and head to diskclearance, present-day HDD sliders are increasingly more susceptible tocontaminant droplet pick-up or other disturbances.

Contaminant build-up on a slider, once large enough, can lead tocontaminants dripping or falling from the slider onto the disk surface,below. This dripping can form a contaminant concentration or “pool,”which may continue to grow and can cause a variety of problems. Toreduce the likelihood of negative performance effects, the contaminantscan be removed, dispersed, or cleaned from the slider surface usingvarious contaminant actuation methods and structures. Contaminantactuation can occur prior to, during, or after substantial build-up ofcontaminants on a slider surface or disk surface below. However,existing methods for cleaning surfaces of a slider, especially a TE,each have significant drawbacks.

Several solutions have been proposed in the past for detection ofcontaminants (e.g., droplets) at the TE and for actuation or removal ofthe contaminants (e.g. dual-ended temperature coefficient of resistance[DETCR] and capacitance-based detection). Some examples of existingmethods of removal include TE micro-channel, electrowetting,self-assembled monolayer (SAM) hydrophobic coatings, SAM patterning,among others.

Although some solutions exist for removal of TE contamination, theexisting solutions suffer from various disadvantages and drawbacks. Somedrawbacks include long times for removal of the contaminants (e.g. byelectrowetting, SAM patterning, etc.), or risk of blocking channels(e.g., a TE micro-channel) for contaminant removal. In some existingcases, suspension of normal drive operation can be necessary for aduration that is long enough to remove the contaminants by externalactuation. Once the drive operation is suspended, the contaminants canbe removed with a fast seek-settle outside a read/write zone of a head,electrowetting on dielectric (EWOD)-based actuation, among othertechniques.

Due to the nature of existing methods of contaminant sensing, noise andprecision issues are often present, which can lead to undesirably lowsignal-to-noise ratios (SNRs) during contaminant sensing, which can havea negative impact on head read/write performance. One example cause oflow SNR during sensing in the existing art can include temperaturesensitivity of DETCR-based TE contaminant sensing, among others.

Thus, existing methods for removal of contaminants from various surfacesof a slider, such as the TE, suffer from drawbacks such as slow responsetimes and undesirable suspension of operations during cleaningoperations. Therefore, the problem of contamination and lubricantbuild-up on the TE of a slider has led to a need and desire for improvedmethods and systems for the removal of harmful contaminants from aslider surface without also correspondingly affecting HDD read/writeoperations.

SUMMARY

The present invention overcomes various disadvantages and shortcomingsof the prior art relating to performance roadblocks to slider and diskdrive technology. Through disclosed methods and structures, magnetichead slider TE sensing and actuation of contaminants can be improved byemploying surface acoustic wave-based sensing and actuation ofcontaminant and lubricant droplets. Actuation of contaminants caninclude displacing, removing, or otherwise interacting with contaminantswith the surface-acoustic wave. High-sensitivity and high-fidelitydetection and efficient actuation or removal of contaminants can thus beachieved.

One benefit of the described methods and structures includes a highfidelity of contamination detection and fast removal compared toexisting methods. Other benefits includes more power-efficientcontamination removal schemes when compared to existing active removalschemes.

According to a first aspect of the present disclosure, a method isdisclosed. The method includes producing a first surface acoustic wave(SAW) on a magnetic head slider using a first interdigitated transducer(IDT), wherein the SAW has a first set of wave characteristics. Themethod also includes receiving the first SAW at a second IDT on themagnetic head slider. The method also includes analyzing the SAW for asecond set of wave characteristics. The method also includesdetermining, based on the analyzing, that a substance having at leastone characteristic is located in a path of the SAW on the magnetic headslider.

According to a second aspect of the present disclosure, a head sliderapparatus for use in a hard-disk drive is disclosed. The apparatusincludes a controller in communication with a first interdigitatedtransducer (IDT) and a second IDT. The apparatus also includes a leadingedge, a trailing edge, and an air bearing surface The apparatus alsoincludes the first IDT being located on the trailing edge and having afirst interdigitated spacing configured to interface with apiezoelectric substrate to create a first surface acoustic wave (SAW)having an first wavelength and an first amplitude. The apparatus alsoincludes the second IDT configured to receive the first SAW created bythe first interdigitated transducer, the received first SAW having asecond wavelength and second amplitude. The apparatus also includes thatthe controller is configured to analyze the received first SAW bycomparing the second wavelength to the first wavelength and the secondamplitude to the first amplitude, to determine whether a contaminant islocated on the trailing edge.

According to a third aspect of the present disclosure, a head sliderapparatus for use in a hard disk drive is disclosed. The apparatusincludes a controller in communication with a first interdigitatedtransducer (IDT) and a second IDT. The apparatus also includes a leadingedge, a trailing edge, and an air bearing surface. The apparatus alsoincludes the first IDT being located on the air bearing surface andhaving a first interdigitated spacing configured to interface with apiezoelectric substrate to create a first surface acoustic wave (SAW)having an first wavelength and an first amplitude. The apparatus alsoincludes the second IDT configured to receive the first SAW created bythe first interdigitated transducer, the received first SAW having asecond wavelength and second amplitude. The apparatus also includes thatthe controller is configured to analyze the received first SAW bycomparing the second wavelength to the first wavelength and the secondamplitude to the first amplitude, to determine whether a contaminant islocated on the air bearing surface.

According to a fourth aspect of the present disclosure, a method isdisclosed. The method includes receiving a first set of wavecharacteristics. The method also includes determining, based on thefirst set of wave characteristics, that a substance having at least onecharacteristic is located on a trailing edge surface of a magnetic headslider. The method also includes producing a first surface acoustic wave(SAW) on the trailing edge surface of the magnetic head slider using afirst interdigitated transducer (IDT), based on the first set of wavecharacteristics such that the substance is actuated.

BRIEF DESCRIPTION OF THE DRAWINGS

Other important objects and advantages of the present invention will beapparent from the following detailed description of the invention takenin connection with the accompanying drawings.

FIG. 1 is a schematic representation of a head/disk interface withultra-small spacing showing contaminant droplets that are picked up ontoa flying slider, which affects the flying characteristics and read/writeperformance of a hard-disk drive.

FIG. 2A-2B are schematic representations of an IDT located on thesurface of a substrate, according to various embodiments.

FIG. 3 is a conceptual representation of a surface-acoustic wave (SAW)device utilizing a SAW to actuate or sense a contaminant droplet,according to various embodiments.

FIG. 4 is a perspective diagram showing a propagating leaky SAWactuating a contamination droplet, according to various.

FIG. 5 is a representation of various power levels of a SAW as appliedto a contaminant droplet, according to various embodiments.

FIG. 6 is a first embodiment of a TE of a slider configured to use SAWsto sense contaminants droplets located on the TE.

FIG. 7 is a second embodiment of a TE of a slider configured to use SAWsto sense and/or actuate contaminant droplets located on the TE.

FIG. 8 is a third embodiment of a TE of a slider configured to use SAWsto sense and/or actuate contaminant droplets located on the TE.

FIG. 9 is a fourth embodiment of a TE of a slider configured to use SAWsto sense and/or actuate contaminant droplets located on the TE.

FIG. 10 is a cross-sectional view of an example wave guiding layer of asubstrate for use in a TE with a SH-SAW wave propagation.

FIG. 11 is a generalized embodiment of a TE oscillator circuit of aslider configured to use SAWs to sense contaminant droplets located onthe TE.

FIG. 12 is an embodiment of a TE configured to use a differential schemefor common-mode noise and thermal compensation.

DETAILED DESCRIPTION

The foregoing specific embodiments of the present invention as set forthin the specification herein are for illustrative purposes only. Variousdeviations and modifications may be made within the spirit and scope ofthe invention without departing from the main theme thereof.

FIG. 1 is a schematic representation 100 of a head/disk interface (HDI)with ultra-small spacing showing contaminant droplets 118 that can bepicked up onto a flying slider 114, as described below. The contaminantdroplets can affect the flying characteristics and read/writeperformance of a hard-disk drive (HDD).

During HDD operation, as described above, a slider 114 flies over aspinning magnetic disk 122, creating some separation called a flyheight. The slider 114 is pivotably mounted to a load beam 110 using aflexible head suspension 112 (shown conceptually and not necessarily toscale). The flexible head suspension 112 may include various flexuresand/or gimbals, as known. The surface of the spinning magnetic hard disk120 may optionally include a carbon overcoat located at a top surface ofthe hard disk 120. An example carbon overcoat may be a diamond-likecoating (DLC) and may be extremely smooth. The carbon overcoat may serveas a corrosion and wear barrier to the recording medium (magnetic disklayer), below. The slider 114, as shown, is angled to fly above thesurface of the hard disk 120. As shown, the hard disk 120 is configuredto be spun (e.g., by a motor, not shown) in the rotational directionshown by arrow 122 (from left to right).

Contaminant droplets 118 composed of various substances can be presenton the surface of the hard disk 120 (and therefore on a carbon overcoatof the hard disk 120 surface, if present) within an HDD, as describedabove. When a slider 114 moves relative to the spinning hard disk 120 indirection 122, contaminant droplets 118 may gather on an ABS 115 and/ora TE 116 (having a TE surface) of the slider 114. Gathered or “pooled”contaminant droplets 118 may disrupt normal or ideal read/writeoperation for various reasons. Various contaminant droplets 118 may bepresent in the HDD intentionally, incidentally, and/or unavoidably,depending on specification and/or environmental factors. Therefore, asdescribed herein, there is a desire to devise new ways to keep headsurfaces (e.g., ABS 115, TE 116) of the slider 114 clear enough of theaforementioned contaminant droplets 118, for effective HDD operation,where possible.

As depicted, contaminant droplets 118 tend to accumulate at an area ofthe slider 114 near the intersection of TE 116 and the ABS 115.Accumulation on these surfaces may then form larger build-ups ofcontaminant droplets 118 or other contamination build-up (as shown onslider 114 at intersection with contaminant droplets 118 near the harddisk 120 surface) as accumulation continues. The build-up on the ABSand/or TE may have a direct effect on the read/write performance of theslider 114, including a loss of precision and an increase in noiseduring operation. Contaminant droplets 118 may include various endgroups and lubricants 124, such as perflouropolyether (PFPE), accordingto various embodiments.

Following cumulative contaminant droplet slider 114 pick-up at ABS 115and/or TE 116, contaminant droplets 118 can become increasingly built-upand more likely to then drop from the slider 114 to the hard disk 120surface, below, particularly if the slider 114 is disturbed. Althoughcontaminant droplets 118 can be picked up by the slider 114, thecontaminant droplets can therefore also drop back to the surface of thehard disk 120 at various times. Contaminant droplets 118 may beespecially prone to drop to the hard disk 120 surface duringdisturbances due to sudden accelerations, including shock and/orvibration events. In particular, if and when the contaminant droplets118 fall to the hard disk 120 surface, the contaminant droplets 118 canform substantial puddles that can then harmfully interact or interferewith the protruded TE 116 of the slider 114, e.g., during read/writeoperation. Example consequences due to interference with the protrudedTE 116 of the slider 114 include skip-write errors and retries for read,which can adversely affect data integrity and slider 114 read/writeperformance.

Indirectly related to slider 114 read/write operation are the flyingcharacteristics of slider 114, which can also be affected due to thecontaminant droplet 118 build-up on the TE 116 and/or ABS 115. As isknown, very small variations to the ABS of slider 114 can havesubstantial impacts on the flying characteristics, such as slider 114pitch and roll. Through changes to the aerodynamic contours of theslider 114, aerodynamic precision and controllability of the slider 114can be substantially negatively affected. As shown and described,sensing of contamination at the TE 116 and subsequent corrective actionsfor removal of the contaminant droplets 118 is therefore of significantimportance.

FIG. 2A-2B are schematic representations of an IDT 210 located on thesurface of a substrate 214.

Example IDT 210 represents a microelectromechanical system (MEMS)configured to produce (and/or receive) a mechanical or surface acousticwave (SAW) in a substrate 214 or on a surface thereof. A SAW is a typeof acoustic wave that travels primarily along a surface of a substrate214 of a solid substance that has a degree of elasticity, e.g., alongdirections depicted by arrows 212. The elastic substance of substrate214 may preferably be a piezoelectric substance. The substance orsubstrate 214 may be a thin film or a bulk substance, according tovarious embodiments. A SAW (e.g., as shown in FIGS. 3 and 4) has acharacteristic of variable amplitude, where the amplitude is greatest atthe surface of the elastic substance, and least at greater depths intothe sub stance.

In general, a mechanical displacement of a substance due to a SAW decaysexponentially away from the surface, so that most (e.g., more than 95%)of the energy of the SAW is configured within a depth equal to onewavelength of the SAW. When a SAW is produced by an IDT, generally anelectromagnetic (EM) radiation signal or waveform is also created at theIDT, and radiates or is transmitted therefrom. SAWs typically travel ata speed on the order of 3,000 meters per second through the substrate214, meaning that the SAW travels much slower than the associated EMradiation, such that a delay line can be formed to compare a time of anIDT receiving a SAW and the associated EM transmission. A delay line, asused herein, can be defined by a space between two IDTs, across which aSAW may travel, e.g., on a slider trailing edge. This space has alength, and a SAW travels the length more slowly than its EM form,causing a measurable delay which may serve various functions.

An input electrical signal can be transduced by IDT 210 into a SAW,which can be affected by and used to sense or detect various physicalphenomena. Either the same IDT 210 or a second IDT (not shown) thentransduces the same SAW back into an electrical signal, at which pointvarious changes to wave characteristics of the SAW, e.g., amplitude,phase, frequency, time delay, and direction of propagation can beinterpreted and compared to the initial or first SAW wavecharacteristics. By comparing the initial or first to the final orsecond SAW wave characteristics, a presence of a physical phenomenon canbe measured and analyzed according to various suitable methods, asappropriate.

As shown with respect to FIG. 2A, IDT 210, is a device configured toproduce or receive a SAW that can be guided, restricted or otherwisemodified or manipulated while propagating. IDT 210, as shown, includestwo interleaved arrays of electrodes 220, 222 seen in FIG. 2A from aperspective surface view and seen in FIG. 2B from a side profile view.The interleaved arrays of electrodes 220, 222 may be made of a metalfilm, and may be deposited on the piezoelectric substrate 214. Thewidths of the individual electrode protrusions may preferably equal theinter-electrode width gaps, which may maximize conversion of electricalto mechanical signal, and vice-versa. In other words, the widths of theindividual protrusions the electrodes 220, 222 may preferably be similarto the separation distance between the protrusions. An exampleprotrusion width may be roughly 0.3 micrometers, which may permit IDT210 to transmit or receive a 3 gigahertz (GHz) frequency. Thepiezoelectric substrate 214 may be made of quartz, lithium niobate,lithium tantalite, zinc oxide, or bismuth germanium oxide, among others.The various substances that make up the substrate 214 may have variouspiezoelectric coupling coefficients and/or temperature sensitivities,depending on the application.

IDT 210 can form a one-port resonator, and therefore can optionally bothproduce and receive a SAW, or take the form of a delay line, employingtwo IDTs (see FIG. 3) paired such that one IDT produces and one IDTreceives the SAW. Input and output IDTs may be substantially similar orsignificantly different based on various applications and functions.Differences may include electrode (e.g., electrode protrusion) overlaps,electrode numbers, and/or electrode positioning, among others. IDTelectrodes 220, 222 may be composed of metal and may form a structureresembling a pair of interlocking combs, each with a plurality ofelectrode protrusions, as shown. IDT 210 has an electrode protrusionspacing (i.e., electrode aperture pitch) and associated transmissionwavelength, λ 216, as shown, which is defined by the spacing andformation of the electrodes. λ 216, according to the shown embodiment,is defined as the distance from two adjacent, like-charge electrodeprotrusions. The electrodes may be disposed on the surface of apiezoelectric substrate 214, such as quartz (SiO₂) or lithium niobate(LiNbO₃), to form a periodic structure. Alternatively, IDT 214 may bedisposed within a substrate 214, which may be a bulk wafer and/or (e.g.,piezoelectric) substance.

In some embodiments, IDT 210 may be configured to convert electricsignals to SAWs by generating periodically-distributed mechanical forcesvia a piezoelectric effect. The generation of a SAW by IDT 210 mayrepresent an input IDT. Conversely, the same principle in reverse may beapplied to convert the SAW back to an electric signal. The receipt andconversion of the SAW may represent an output IDT. These processes ofgeneration and reception of SAW can be used in different types of SAWsignal processing devices, such as band pass filters, delay lines,resonators, sensors, etc., as known.

According to various embodiments, IDT 210 can form part of a so-calleddelay line, as described herein, in which electrodes 220, 222 arepreferably uniformly spaced such that the phase is a linear function ofthe frequency. According to other embodiments, IDT 210 can form part ofa SAW resonator, where IDTs are used to convert electrical to mechanicalsignals, and vice-versa (but do not receive amplitude and phasecharacteristics). In a resonator, one or more SAW “acoustic” reflectorsmay be used with a single IDT (e.g., IDT 210), where metal stripes orgrooves of a depth reflect a SAW (seen best in FIG. 6), whereas delaylines typically utilized at least two IDTs.

FIG. 2B illustrates an example cross-sectional view 202 and an electricfield map produced in a piezoelectric substrate 214 between positive 220and negatively-charged 222 electrodes of IDT 210, with a characteristicwavelength λ 216, equivalent to a regular spacing between two nearest,like-charge protrusions of a single polarity electrode (separated by anoppositely-charged electrode protrusion), either positive 220 ornegative 222, as described above. Electric field lines 218 are shownpointing from positive 220 to negative 222 electrodes, which form analternating pattern every wavelength λ 216. Electric field lines 218, asshown, may pass through substrate 214.

FIG. 3 is a conceptual representation of a SAW device 300 utilizing aSAW 316 to actuate or sense a contaminant droplet 318, according tovarious embodiments.

A SAW device 300 layout, as shown may be a delay line. The delay lineincludes two IDTs (input IDT 310 and output IDT 320) located on apiezoelectric substrate 324. As shown, an input IDT 310 has an electrodeprotrusion spacing of λ 312, and substrate 324 has an inter-IDT spacingof L 322, which preferably represents a distance that a SAW 314 willtravel between IDTs 310 and 320. According to one delay line embodiment,input IDT 310 begins by transmitting a SAW 314 having a first set ofwave characteristics, and an output IDT 320 then receives a leaky SAW316 having a second set of wave characteristics.

Still with reference to FIG. 3, the leaky SAW 316 is created by SAW 314interacting with contamination droplet 318 located on the surface ofsubstrate 324. The input IDT 310 with an initial radio frequency (RF)voltage input can create SAW 314 on piezoelectric substrate 324. Theoutput IDT 320 then preferably senses the leaky SAW 316 and converts thereceived wave characteristics into an oscillatory (e.g., RF) voltagesignal using known methods and/or systems.

When a contaminant droplet 318, e.g., in bulk, lies on the propagationpath of an emitted SAW, the SAW changes mode into a leaky SAW and dampsexponentially when reaching the contaminant droplet 318. The contaminantdroplet 318, in some example, includes an oil-based substance. A leakySAW denotes a SAW that has at least one characteristic, such asamplitude, frequency, phase, or time delay, which measurably attenuatesin the presence of a contaminant droplet 318 (or other liquid) dropletor film on the substrate 324. Changes to amplitude, frequency, etc., forexample, can be sensed and analyzed. Once analyzed, the presence,location, and characteristics of contaminant droplet 318 on thesubstrate surface can be detected, and appropriate methods andprocedures for contaminant droplet 318 removal can be determined ordeduced.

As used herein, actuation as used with respect to one or morecontaminant droplets 318 on a TE or other slider surface, can involveusing properties in SAWs to physically affect the contaminant droplet318 in various ways. Preferably, actuation of the contaminant droplet318 can caused the contaminant droplet 318 to be removed or displacedfrom the TE or order slider surface. In other embodiments, the actuationof the contaminant droplet 318 on the surface can involve moving,reshaping, heating, or otherwise affecting the contaminant droplet 318or any constituents thereof. By using a SAW 314 for actuation of acontaminant droplet 318, longitudinal pressure waves may be created byinput IDT 310 and may propagate into the contaminant droplet 318 at anangle such that the contaminant droplet 318 is actuated. In one example,the angle that the SAW propagates into the contaminant droplet 318 canbe a Rayleigh angle (θ_(R)) defined as θ_(R)=sin−1 (C_(liquid)C_(s)),where C_(s) is the SAW 314 velocity in the substrate 324. Rayleigh waveshaving Rayleigh angles are described in greater detail with reference toFIG. 4, below.

As the SAW propagates into the contaminant droplet 318, the SAWpreferably radiates pressure waves in order to induce an acoustic forcein the contaminant droplet 318, which can result in actuation in theform of a bulk liquid circulation (e.g., heating, see also FIG. 4)within the contaminant droplet 318. With or without the bulk liquidcirculation, actuation can also take the form of acoustic streaming, orthe movement of the contaminant droplet from one location to another.Upon the contaminant droplet 318 receiving the actuating SAW 314 fromthe input IDT 310, the contaminant droplet 318 can be actuated at anacoustic streaming propulsion rate (speed) of up to several mm/sec,according to various embodiments.

Wavelength λ 312 can be equal to a width or pitch of IDT 310 (as shown)and SAW frequency is f₀=v/λ, where v=velocity of sound in thepiezoelectric substrate 324. According to one embodiment, RF oscillationfrequency may be set to f₀ for maximum SAW 314 excitation, actuation, orpropagation efficiency. As used herein, the SAW 314, as it propagatesacross substrate 324, may take an amount of time to arrive at output IDT320 from the input IDT 310, with a delay line time of t=L/v in a delayline example.

A presence of a contaminant droplet 318 in the SAW 314 acoustic pathwaycauses change in SAW 314 velocity, “v” (in addition to SAW 314 amplitudechange), resulting in signal delay (dt) and therefore frequency shiftdf˜dt that can be detected, according to various embodiments.

FIG. 4 is a perspective diagram 400 showing a propagating leaky SAW 418actuating a contamination droplet 410.

A Rayleigh wave is a type of SAW that travels near the surface of asolid, such as a piezoelectric/substrate layer 424 of a slider. Rayleighwaves can be produced using piezoelectric transduction, such as using anIDT as described herein. IDT can radiate a longitudinal Rayleigh wave(SAW) 416 into a liquid contaminant droplet 410 when a SAW 416propagates at the liquid/solid interface. As shown, air 422 or othersurrounding gas or fluid can be located above the substrate 424, asshown. The density of the air 422 can affect the properties of theRayleigh wave 416. The Rayleigh wave 416 may exert a force (F) on acontaminant droplet 410. The force exerted by the Rayleigh wave 416 canbe defined by the following formula:F==ρ(1+α²)^(3/2) A ²ω² k _(i) exp 2(k _(i) x+αk _(i) y).

And, the amplitude of the SAW 416 at a point of interaction, at whichpoint SAW 416 preferably becomes a leaky SAW 418, with contaminantdroplet 410 can be defined by the following formula:

A/λ = 8.15 × 10⁻⁶P_(D)^(0.225) + 5 × 10⁻⁶P_(D)^(0.8)

Where P_(D) is SAW 416 input power, and α=acoustic absorption factor.

When the Rayleigh wave (SAW) 416 input power (either measured at theinput IDT or the wave itself) is increased beyond a “critical” value,e.g., by passing higher voltage through an input IDT that produces theRayleigh wave, the wave may cause a pressure gradient inside thecontaminant droplet 410 to be larger than the surface tension (as afunction of the properties of the contaminant droplet 410 and the air422). At the critical value of the input power of the Rayleigh wave, thecontaminant droplet 410 can be moved along a wave propagation direction(to the right, as shown), which can have an associated Rayleigh angle(θ_(R)), described with reference to FIG. 3, above. Various SAW 416input power levels can have different effects on a contaminant droplet410, such as causing a recirculation 414 (e.g., heating), and astreaming 412 of the droplet 410. At a point of interaction with thedroplet 410, the SAW 416 may become a leaky SAW 418, as describedherein. Further variations of effects of SAW-droplet interaction can befurther seen with respect to FIG. 5. The force (F_(s)) necessary toovercome the liquid surface tension is given by:

$F_{s} = {2\; R\;\gamma\;{lv}\;{\sin\left( \frac{\theta_{a} + \theta_{r}}{2} \right)}\left( {{\cos\;\theta_{r}} - {\cos\;\theta_{a}}} \right)}$

According to various embodiments, an advancing Rayleigh angle (e.g.,θ_(R)=80°), may be typical for viscous fluids on a solid substrate (orfilm) 424, e.g., ZnO. A maximum surface tension of a contaminant droplet410 may be roughly 0.0008 millinewtons (mN) for a contaminant droplet410 with a diameter of 40 micrometers and seven micrometers in height.Also, according to the formula, as Rayleigh (SAW) 416 power increases,contact Rayleigh angle 420 hysteresis (θ_(a)θ_(r)) also increases andthe contaminant droplet 410 can move to minimize its own interface withthe solid substrate 424. As the contaminant droplet 410 moves, thecontaminant droplet 410 can be actuated (e.g., moved) along the x-axis,as shown, and therefore caused to be removed from the solid substrate424. Conversely, if Rayleigh wave 416 power decreases, the contact angle420 hysteresis can also decrease. At lower Rayleigh wave 416 power, theactuation of the droplet 410 can include recirculation and/or streamingof the droplet 410, as shown, and as further described with respect toFIG. 5, below.

An approximation of propulsive force (F_(stream)) applied to thecontaminant droplet 410 can also be expressed as:

$F_{{stream}\;} = {{\alpha\left( {V - V_{thresh}} \right)}^{2}\left( \frac{\sin\;{\beta\left( {V - V_{thresh}} \right)}}{\left( {V - V_{thresh}} \right)} \right)^{2}}$

In various embodiments, and according to the above formulas,approximately 2-3 V of applied RF voltage at 250 MHz frequency can meetthe voltage threshold (V_(thresh)) that causes propulsion of thecontaminant droplet 410, e.g., in the form of removal toward varioussides of a TE. According to some embodiments, once the contaminantdroplet 410 starts moving, viscous dissipation of the SAW energy withinthe droplet 410 volume as well as shear stress at a droplet-substratecontact may affect results.

An amplitude (A) of an example SAW can have an amplitude expressedempirically as:A=λ(8.15×10^(−6 p0.225)+5×10^(−6 p0.8))

Likewise, SAW energy transmitted per second (E_(in)) to the contaminantdroplet 410 can be expressed as:E _(tn)=(2π² dpρ _(f) V _(R) ³ A ²)/λ

According to various embodiments, inside the contaminant droplet 410,the SAW 416 amplitude can decay in the direction of propagation (here,to the right). Typically, the decay is 1/e of incidental value overseveral SAW wavelengths. According to testing, average energytransferred to the contaminant droplet 410 can be approximately 50% ofthe total wave energy. Furthermore, a SAW attenuation factor can begiven by:

$\alpha_{L} = \frac{\rho_{f}V_{f}}{\rho\; V_{R}\lambda}$

An estimate of contaminant droplet 410 propulsion speed (V_(propulsion))can be expressed as a function of applied (RF) SAW power, as:

$V_{propulsion} = {\left( {{- F_{S}} + \sqrt{F_{S}^{2} + {4\;\beta\; E_{avg}}}} \right)\text{/}2\;\beta\mspace{14mu}{Where}\text{:}}$$\beta = {{\mu\left( \frac{\pi\; d^{2}}{4} \right)}\text{/}\left( {h/2} \right)}$

For the above, P=applied (RF) SAW power, L=SAW wavelength, ρ_(f)=densityof contaminant droplet 410, ρ=density of (e.g., ZnO) film, V_(R)=SAWspeed in film, A=SAW amplitude, d=contaminant droplet 410 diameter,h=height of contaminant droplet 410, μ=contaminant droplet 410viscosity, V_(f)=acoustic speed in contaminant droplet 410, andF_(S)=surface tension of contaminant droplet 410.

FIG. 5 is a representation of various power levels 500 of a SAW asapplied to a contaminant droplet (e.g., contaminant droplet 410 of FIG.4), according to various embodiments.

As described with respect to FIGS. 3 and 4 in particular, a contaminantdroplet (e.g., 318, 410) may be located and sensed on a surface of apiezoelectric substrate 518. Various SAW power levels during actuationhave varying effects on an example contaminant droplet, and arrow 520represents increasing SAW power for actuation, from left to right. SAWsused for sensing would have lower power levels than shown with respectto FIG. 5 so as to detect the contaminant droplet without immediatelyactuating it. Logically, as greater amounts of power and force areapplied to a contaminant droplet, the SAW tends to cause greateractuation of the contaminant droplet.

At 510, a low SAW power level causes a contaminant droplet to vibrate orcirculate (e.g., heating). At 510, the droplet may not displace oractuate to the point of being removed from substrate 518, but thedroplet may undergo internal shifting and movement. At 512, an increased SAW power level causes the droplet to actuate or move by the forcesdescribed above, such as may be used to shift contamination from onearea of a surface to another. At 514, further increased SAW power, asshown, causes droplet jetting. Droplet jetting occurs when a droplet onthe substrate 518 to become airborne and displace at least partiallyvertically, e.g., due to power transferred to the droplet via SAW thatexceeds a surface tension of the droplet. At 516, which can represent aneven high incident SAW power than 514, a contaminant droplet isatomized. Droplet atomization occurs when the droplet receives a veryhigh power SAW, and the droplet's surface tension is heavilydisintegrated, separating the droplet into very fine particles. If thedroplet is atomized in this way, subsequent contaminant droplet build-upand reconstitution on the surface are relatively less likely to occur inthe future.

Turning now to FIGS. 6-12, various slider TE configurations and viewsare shown. In the various configurations, bond pads 10 are typicallylocated near the top of the TE (as shown), and electronic lapping guides(ELGs) 12 are shown below the bond pads 10. At the top of the TE can bea surface, referred to herein as a TE surface. The area of a TE locatedbelow ELG 12 is the primary area of focus of this disclosure, with thenotable exception of FIG. 12.

As described herein, one or more IDTs can be located on or in a slider,and in particular on or in a slider TE. FIGS. 6-12 shows IDT(s) asvisible, and according to various embodiments the IDT(s) can be visible,hidden, or visible only using certain equipment. As described below, theIDT and SAW-based structures and devices can be manufactured accordingto various methods and structures, as suitable. Preferably, embodimentsdescribed herein use surface-based Rayleigh waves, which can benefitfrom IDTs being located on or near a TE surface, but according to otherembodiments, Lamb or other waves (multiple wave layers, or waves below asurface) can be used, and the IDTs can be located further beneathvarious slider surfaces, including a TE. For the purposes ofillustration, the various IDTs, reflectors, and other components areshown as being visible, but this is not to be construed in a limitingsense and is shown for illustrative purposes.

In particular, two basic approaches are considered for the fabricationof slider and other device configurations, as described herein. A firstapproach includes fabricating a device (e.g., an IDT) as a thin-filmsensor (e.g., ZnO, AlN, PZT, etc.). This approach may be similar todepositing one or more IDTs on a thin-film piezoelectric substrate of aslider. Once deposited on the substrate, various protective coatings canbe applied over the IDT and any other surfaces or devices. A secondapproach can include fabricating a SAW device (e.g., IDT, etc.)separately, which can be solder bonded to a TE of the slider. Accordingto various embodiments, bulk piezoelectric substrates such as PZT,single-crystal LiTaO₃, single-crystal LiNbO₃, quartz, etc. may bepreferable options for a bulk piezoelectric substrate material. Thesecond approach may provide increased flexibility with respect to designand configuration. Various embodiments may utilize configurations thatcan provide larger acoustic streamlining forces than the firm approachand ZnO-based devices, for instance.

Control of the various sensing/actuation functions of the various IDTsdescribed with respect to FIGS. 6-9 can utilize various controllers thatcan include processors operatively coupled to memory and/or storagedevices in order to perform the various functions described herein.Detectors sense something, decide to remove, etc. Examples of operativeIDT and controller schematic configurations are described in more detailwith respect to FIGS. 11 and 12, but other control schemes can also beapplied, as suitable. In some embodiments, a controller can initiate asensing operation using one or more IDTs, followed by an actuationoperation using the one or more IDTs. The actuation operation canutilize sensed properties of contaminant droplets in order to actuatethe contaminant droplets, according to various embodiments, and asdescribed herein.

FIG. 6 is a first embodiment of a TE 600 of a slider configured to useSAWs to sense contaminants droplets located on the TE 600. The followingembodiments are preferably utilized for detection of contaminantdroplets on the slider TE 600. The TE 600 embodiment shown may be aresonator, according to various embodiments.

According to one variation, an input electrical signal applied to thesingle input/output IDT 610 forms a mechanical SAW (described above) inthe piezoelectric resonator 612 that travels along the surface on both(left and right) sides from the IDT 610 as conceptually illustrated bybi-directional propagation arrows 618. The wave(s) reflect fromreflective arrays 14, 16 (e.g., metal stripes or grooves) and travelback to the IDT 610 after a period of time has elapsed, which transformsthe SAW(s) back to an electrical signal that can then be sensed and/oranalyzed. The presence of a liquid contaminant droplet or film (notshown) may cause attenuation of amplitude of the wave (e.g., in the formof a leaky SAW) as well as change in wave velocity or othercharacteristic. The change in the wave velocity, in particular, mayresult in a signal delay (hence the term delay line, as describedherein), which can be sensed through a frequency change of the receivedwave as compared to the original, transmitted wave.

An example SAW (e.g., a Rayleigh wave) can propagate through mostelastic materials including metals and insulators, without a uniformpiezoelectric or purpose-designed flexible substrate. As a result of theaforementioned SAW property, and according to another variation of theshown layout, the piezoelectric resonator 612 can be confined to becovering just the IDT area (horizontal borders of which are defined asshown by dotted two lines 620), permitting SAWs to exit thepiezoelectric substrate, and pass through other substances, beforere-entering the piezoelectric substrate.

According to a third variation of the shown layout, IDT 610 can producea shear-horizontal (SH)-SAW where a wave has shearing wave propertieshorizontally with respect to a surface of propagation. An SH-SAW mayhave lower radiation losses into a liquid contaminant droplet or layerwhen compared to a Rayleigh wave. A SH-SAW may also have improvedsensitivity to contaminant droplet detection. To generate a SH-SAWinstead of a Rayleigh wave, the substrate construction depicted in FIG.10 can be adopted to the sensing region.

According to various embodiments, an IDT 610 (or other IDTs, herein) canhave a particular geometry. The IDT 610 geometry can maximize an IDT 610aperture (i.e., length), however space for the IDT 610 can beconstrained by bond-pads and/or ELG pads located below the IDT 610. Inaddition, a “center” frequency (F₀) can be chosen for the IDT 610 to bemaximized without contaminating a writer, reader, or other sensorsignals of an associated slider. This can be referred to as frequencyseparation.

According to one preferable example, f₀=250 MH, SAW velocity in Zn) is2,700 m/s, IDT 610 pitch and SAW wavelength are 10.8 micrometers, IDT610 thickness is half of a corresponding substrate thickness, or about1-2 micrometers, the IDT 610 length is about 30 micrometers, and the IDT610 width is about half the IDT 610 pitch, or about 5.4 micrometers.Many variations of the above are contemplated herein.

FIG. 7 is a second embodiment of a TE 700 of a slider configured to useSAWs to sense and/or actuate contaminant droplets located on the TE 700.The following embodiments are preferably utilized for detection oractuation of contaminant droplets on the slider TE 700 and may form adelay line configuration, as described herein.

TE 700 can be similar to TE 600, but includes a pair of IDTs 712, 714,as well as optional micro-channel wave guides 18. Micro-channel waveguides 18, if present, may guide and direct a propagating SAW throughconfinement and added pressure gradient due to a so-called “capillary”effect. As shown, if a contaminant droplet (or a contaminant layer) ispresent on TE 700, the contaminant droplet may attenuate an incoming SAWamplitude sensed at output IDT and may also cause a frequency shift inthe SAW delay line (defined by a distance in a substrate through whichthe SAW travels), which can be used for contaminant-sensing purposes.

In other embodiments where optional micro-channel wave guides 18 areomitted and droplet actuation is desired, a large enough input powerfrom IDT 712 to the sensed contaminant droplets (if present) can beapplied via SAW 720, propelling the contaminant droplets away along thedirection of wave propagation 720 using acoustic streaming, towards theside faces (left and right edges of the TE, as shown) and away from theinput IDT 712.

According to one embodiment, a delay line 718 (located between IDT 712and IDT 714) can include coated piezoelectric substrate or film with ahydrophobic coating configured to reduce surface energy, and therebylowering the power required for SAW-based actuation. Various coatingscan also be present during sensing operation, according to variousembodiments. Examples of hydrophobic coatings that may be utilizedinclude SAM, graphite fluoride (a-CFx), polyvinylidene fluoride (PVDF),or polytetrafluoroethylene (PTFE), among others.

According to various embodiments, the roles of input 712 and output 714IDTs can be interchanged, but one configuration has been shown as anexample. Through a determination of the nearest side face (left orright), the opposite-end IDT can be configured to be the input IDT inorder to propel the contamination droplets towards the nearest side face(i.e., along a shorter distance), away from the input IDT. In so doing,expulsion of contaminant droplets from TE region may be expedited.According to various embodiments, sensing and input circuitry may needto be duplicated at both respective TE ends, which may add complexity tovarious embodiments.

As in FIG. 6, Rayleigh waves can propagate effectively through mostelastic materials including metals and insulators (e.g., aluminum), andthe piezoelectric layers can be confined to just the regions beneathand/or surrounding the input/output IDTs 712/714. Also as in FIG. 6,SH-SAW waves may have lower radiation losses into a liquid contaminantdroplet or layer, and may have better improved sensitivity tocontaminant droplet detection. To generate SH-SAW instead of Rayleighwave, the substrate construction depicted in FIG. 10 can be adopted tothe sensing region.

FIG. 8 is a third embodiment of TE 800 of a slider configured to useSAWs to sense and/or actuate contaminant droplets located on the TE 800.The following embodiments are preferably utilized for detection and/oractuation of contaminant droplets on the slider TE 800.

Shown in a three-IDT TE layout, where one, central input IDT 810 islocated approximately midway between two output IDTs 812, 814.Propagating SAWs 816 are shown traveling between central input IDT 810and the two output IDTs 812, 814. Using the shown configuration, thepresence of contaminant droplets on either half of the slider width canbe effectively sensed. SAWs 816 produced by IDT 810 can propelcontaminant droplets (not shown) away from the IDT 810 using acousticstreaming (sufficiently high power input applied to input IDT at thecenter) along both directions, as described herein.

Micro-channel wave guides 18, as shown and described with respect toFIG. 7, may guide and direct a propagating SAW through confinement andadded pressure gradient due to a so-called “capillary” effect. As shown,if a contaminant droplet (or a contaminant film or layer) is present onTE 800, the contaminant droplet may attenuate SAW amplitude sensed atoutput IDT and may also causes a frequency shift in the SAW delay line(distance in substrate through which the SAW travels), which can be usedfor contaminant-sensing purposes.

Even if optional micro-channel wave guides 18 are omitted, applying alarge enough input power to the sensed contaminant droplets (if present)can be propelled away along the directions of wave propagation 716 usingacoustic streaming, towards the side faces and away from the centralinput IDT 810.

As described with respect to FIG. 7, the piezoelectric delay line(s) 818can be a coated piezoelectric substrate or film with a hydrophobiccoating (as described, above) configured to reduce surface energy, andthereby lowering the power required for SAW-based actuation. The delayline(s) 818, as shown, can be located between IDT 810, 812, and/or 814.

FIG. 9 is a fourth embodiment of a TE 900 of a slider configured to useSAWs to sense and/or actuate contaminant droplets located on the TE 900.The following embodiments are preferably utilized for detection oractuation of contaminant droplets on the slider TE 900.

TE configuration 900 is conceptually and structurally similar to acombination of the layouts shown with respect to FIGS. 6 and 8. Using atwo-IDT configuration with a center input/output IDT 910 similar to theconfiguration of FIG. 8, one of the output IDTs is replaced instead withan acoustic reflector 16, as described in FIG. 6. The acoustic reflectormay be a metal stripe or groove and may be configured to reflect a SAWfrom IDT 910 back to IDT 910.

By employing such a hybrid configuration (combining a delay line 922 andresonator 920 configuration), contamination droplets can be sensed oneither half of the slider TE width using the direct-incident (two IDTs910, 912) and reflected SAW (IDT 910 only). As shown, contaminationdroplets can be propelled away from the central input IDT 910 regionusing acoustic streaming of sufficiently power input applied to centerinput IDT 910, along both directions.

FIG. 10 is a cross-sectional view of an example wave guiding layer of asubstrate 1000 for use in a TE with a SH-SAW wave propagation.

As discussed, since Rayleigh waves can propagate effectively throughmost elastic materials including metals and insulators (e.g., alumina)the piezoelectric layers can be confined to just the regions beneath theIDTs. However, an alternate type of SAW, SH-SAW waves, have lowerradiation losses into a liquid contaminant droplet or layer, and hencemay have better sensitivity to contaminant droplet detection.

To generate a SH-SAW instead of a Rayleigh wave, a construction can beadopted to the sensing region that includes a wave guiding layer 1010,which can be composed of, e.g., SiO2, ZnO, polymer layers, etc., whichmay contain IDT electrodes 1014 within the wave-guiding layer 1010, asdescribed herein. A piezoelectric substrate 1012 is located below waveguiding layer 1010, and may be in contact with IDT electrodes 1014 aswell as the wave-guiding layer 1010.

FIG. 11 is a generalized embodiment of a TE oscillator circuit 1100 of aslider configured to use SAWs to sense contaminant droplets located onthe TE 1100. The following embodiments may be preferably utilized fordetection or actuation of contaminant droplets on the slider TE 1100,and may represent delay line embodiments.

As shown, an oscillator circuit is formed by grounds 18, 20,electrically connected to respective input and output IDTs 14 and 16,along with wiring 30 configured to connect IDT 14 to RF amplifiercomponent 26. An output signal 28 is produced by the input IDT 14amplified output by amplifier 26, when electrically connected to outputIDT 16. The oscillator circuit places a two-port (i.e., a two IDT) delayline SAW piezoelectric device in the feedback loop of an RF amplifier.According to one example, where amplifier 26 has function A(f), anddelay line 24 has function B(f), the condition for the oscillation isA(f)·B(f)=−1, from which |A(f)|·|B(f)|=1 is found for the loop gain andfor the loop phase arg A(f)·B(f)=−2πn, where n is an integer. Accordingto various embodiments, Δf/f₀ (a ratio of change in SAW frequency toinitial frequency) may be proportional to Δv/v₀ (a ratio of change inSAW velocity to initial velocity). By counting or measuring theoscillator frequency with a digital frequency counter may provide aprecise indirect measurement of acoustic wave velocity, which may varyin the presence of a contaminant (e.g., in the form of liquid, droplets,or film), according to various embodiments.

The described methods and configurations, however, may be relativelyinsensitive to signal amplitude and hence may not be as sensitive to acapture effect of contaminant-induced attenuation, according to variousembodiments. The described methods and configurations may rely ondetecting change in acoustic velocity and/or the change in acousticvelocity's effect on signal frequency measured using the oscillatorcircuit at output 28.

FIG. 12 is an embodiment of a slider TE 1200 configured to use adifferential scheme for common-mode noise and thermal compensation,according to various embodiments.

Shown is a variation of a TE differential scheme and configuration thatuses a dual-channel, two-port SAW delay line configuration to compensatefor common-mode noise, thermal effects, and viscosity effects.

Similar to other embodiments, a first, sensor delay line 24 is locatedon a lower end of the TE face. The sensor delay line 24 includes IDTs 14and 16, e.g., with one input IDT and one output IDT. A sensor portion ofa dual-channel circuit is formed by connecting the sensor IDTs 14, 16via sensor wiring 42 to sensor amplifier 30 and eventually outputting asensor signal 50 to a signal mixer 40. The signal mixer 40 may be afrequency mixer or other form of signal mixer, according to variousembodiments.

Notably, in this embodiment, a second, reference SAW two-port delay line38 is added to an upper end of the TE face. The second, reference SAW isshown as located above the bond pads 10 and ELG pads 12. According tovarious embodiment, the reference SAW delay line 38 is locatedrelatively far from a disk surface (not shown), allowing a relativelycontaminant-free operation. The reference delay line 38 has a paralleland matched pair of IDTs 34, and 36 intended to mirror the configurationof the sensor SAW delay line 24, with respective IDTs 14 and 16. Areference portion of a dual-channel circuit is formed by connecting thereference IDTs 34, 36 via reference wiring to reference amplifier 32 andeventually outputting a reference signal 48 to the signal mixer 40.

After the signal mixer 40 receives both the reference output signal 48and the sensor output signal 50, the pair of signals can be compared andanalyzed, and a differential output 46 can be produced. The differentialoutput 46, based on the reference output signal 48 and the sensor outputsignal 50 can be calibrated to reduce and compensate for unwanted signalnoise, such as due to thermal effects, environmental, and other noisefactors through a differential scheme that uses the describeddual-channel delay line configuration, using the sensor SAW delay line24 in parallel with the reference SAW delay line 38. According tovarious embodiments, the reference SAW delay line may preferably be keptin a region not close to a region of interest (e.g., above the bondpads, as in this case).

As used herein, various embodiments described herein utilize variousforms of SAWs. As used herein, SAWs can include Rayleigh waves, asdescribed, but can also include Lamb, Love, flexural plate waves (a typeof Lamb wave). As described, SH-SAW waves can also be generated and usedaccording to various embodiments.

IDTs may preferably be used for SAW generation (and detection of leakySAWs, etc.), as described. However, besides IDTs, wedge & comb-basedtransducers, piezoelectric thin films deposited on a substrate or bulksurface mode conversion using grooves or gratings can also be used.

As described herein, a hydrophobic coating of the transduction ordroplet accumulation region may help increase droplet mobility andtherefore reduce power required for propelling the droplets away fromthe transducer region.

In principle, the concepts described herein can also be used inmitigating contaminant droplet build-up on a slider ABS, howevervariations to implementation may be encountered.

For SAW excitation or propagation, substrates may preferably be formedof PZT, AlN, ZnO, LiNbO₃, LiTaO3, Li₂B4O₇, GaPO₄, Langasite, etc.

Implementation of the proposed schemes and the SAW device structures mayentail or demand variations and modifications to some wafer processsteps and pre-amplification changes. However the changes may be similarin complexity and requirements to the other, existing schemes discussedin the background.

It is understood that numerous variations of SAW-based sensing andactuation of contaminant droplets on a slider could be made whilemaintaining the overall inventive design of various components thereofand remaining within the scope of the disclosure. Numerous alternatedesign or element features have been mentioned above.

As used herein, the singular forms “a,” “an,” and “the” encompassembodiments having plural referents, unless the content clearly dictatesotherwise. As used in this specification and the appended claims, theterm “or” is generally employed in its sense including “and/or” unlessthe content clearly dictates otherwise.

Unless otherwise indicated, all numbers expressing feature sizes,amounts, and physical properties are to be understood as being modifiedby the term “about.” Accordingly, unless indicated to the contrary, thenumerical parameters set forth are approximations that can varydepending upon the desired properties sought to be obtained by thoseskilled in the art utilizing the teachings disclosed herein.

Although certain features are described generally herein relative toparticular embodiments of the invention, it is understood that thefeatures are interchangeable between embodiments to arrive at anSAW-based sensing and actuation, and/or dispersing of contaminantdroplets that includes features of different illustrated embodiments. Itis further understood that although certain embodiments discussed aboveinclude using SAWs on a TE of a slider, other surfaces of a slider orother HDD component may be sensed and/or actuated using the disclosedmethods and structures.

What is claimed is:
 1. A method of determining the presence of acontaminant on a surface of a slider, comprising: receiving a firstsurface acoustic wave (SAW) at a transducer on a magnetic head slider;analyzing the first SAW for one or more wave characteristics; anddetermining, based on the analyzing, that a contaminant having at leastone characteristic is detected on the magnetic head slider.
 2. Themethod of claim 1, further comprising: producing a second SAW using thetransducer, wherein the second SAW is configured to actuate thecontaminant based on the at least one characteristic of the contaminant.3. The method of claim 1, wherein the one or more wave characteristicscomprise a first set of wave characteristics that include: a firstamplitude, a first velocity, a first wavelength, a first phase, and afirst direction of propagation.
 4. The method of claim 2, wherein thesecond SAW comprises a second set of one or more wave characteristicsthat include: a time delay, a second amplitude, a second velocity, asecond wavelength, a second phase, and a second direction ofpropagation.
 5. The method of claim 2, wherein the first SAW is used forsensing the contaminant, and the second SAW is used for actuating thecontaminant.
 6. The method of claim 1, wherein the first SAW is producedon a trailing edge of the magnetic head slider.
 7. A head sliderapparatus for use in a hard-disk drive, comprising: a magnetic headslider comprising a first surface, wherein a first transducer and asecond transducer are located on the first surface; a controller incommunication with the first transducer and the second transducer;wherein the first transducer is configured to create a first surfaceacoustic wave (SAW) having a first set of wave characteristics; whereinthe second transducer is configured to receive the first SAW created bythe first transducer, the received first SAW having a second set of wavecharacteristics; and wherein the controller is configured to analyze thereceived first SAW by comparing the second set of wave characteristicsto the first set of wave characteristics.
 8. The head slider apparatusof claim 7, wherein if the controller determines that a contaminant islocated on the first surface, then the controller is configured to causethe first transducer create a second SAW, and wherein the second SAW isconfigured to actuate the contaminant.
 9. The head slider apparatus ofclaim 8, wherein the second SAW is configured to actuate the contaminantby having a contact angle and power at a time of SAW incidence with thecontaminant.
 10. The head slider apparatus of claim 7, furthercomprising: an acoustic reflector configured to reflect the first SAWfrom the first transducer to the second transducer.
 11. The head sliderapparatus of claim 7, wherein the first transducer and the secondtransducer are the same transducer.
 12. A method for actuating asubstance on a magnetic head slider, comprising: receiving a first setof wave characteristics; determining, based on the first set of wavecharacteristics, that a substance having at least one characteristic islocated on a surface of the magnetic head slider; and producing a firstwave on the surface of the magnetic head slider using a firsttransducer, based on the first set of wave characteristics.
 13. Themethod of claim 12, wherein the first set of wave characteristics isreceived at the first transducer.
 14. The method of claim 12, whereinthe first wave has a second set of wave characteristics, and wherein thefirst wave is used for actuating the sub stance.
 15. The method of claim12, wherein a second wave comprises the first set of wavecharacteristics, and wherein the second wave is used for sensing thesubstance.
 16. The method of claim 12, wherein the first set of wavecharacteristics includes: a first amplitude, a first velocity, a firstwavelength, a first phase, and a first direction of propagation.
 17. Themethod of claim 12, wherein the first wave is a surface acoustic wave(SAW).
 18. The method of claim 12, wherein the first wave on the surfaceof the magnetic head slider is produced such that the substance isactuated.
 19. The method of claim 14, wherein the second set of wavecharacteristics includes: a time delay, a second amplitude, a secondvelocity, a second wavelength, a second phase, and a second direction ofpropagation.